High Blood Pressure (Hypertension)

You might think that high blood pressure (hypertension) just affects adults. But babies, kids, and teens can have it too.

About 1 in 25 teenagers has high blood pressure. In babies, it's usually caused by prematurity or problems with the kidneys or heart. While hypertension is far more common among adults, the rate among kids is on the rise, a trend that experts link to the increase in childhood obesity.

Many kids and teens with high blood pressure have no other health problems but do have a family history of hypertension and an unhealthy lifestyle — a bad diet, excess weight, stress, and too little physical activity.

If it's not treated, high blood pressure can damage the heart, brain, kidneys, and eyes. But when hypertension is caught early, monitored, and treated, kids can lead an active, normal life.

What Is Blood Pressure?

Blood pressure is the force that blood puts on our blood vessel walls as the heart pumps. When the heart contracts and pushes blood into the vessels, blood pressure rises. It lowers when the heart relaxes, but there's always a certain amount of pressure in the arteries.

Two physical forces drive blood pressure — one force comes from the heart as it pumps blood into the arteries and through the circulatory system, and the other is from the arteries as they resist this blood flow.

Blood pressure changes from minute to minute and is affected by activity and rest, body temperature, diet, emotional state, posture, and medications.

Long-Term Effects of High Blood Pressure

When someone has high blood pressure, the heart and arteries have a much heavier workload. The heart must pump harder, and the arteries are under greater strain as they carry blood.

If high blood pressure continues for a long time, the heart and arteries may no longer work as well as they should. Other organs that are receiving the blood, like the kidneys and brain, also can be affected.

Having high blood pressure puts someone at a higher risk for stroke, heart attack, heart failure, kidney failure, loss of vision, and atherosclerosis (hardening of the arteries).

While high blood pressure doesn't always cause symptoms, it still affects the body and puts a person at risk for those long-term health problems. In rare cases, severe hypertension can cause headaches, visual changes, dizziness, nosebleeds, heart palpitations, and nausea.

If your child has severe high blood pressure and has any of these symptoms, seek medical care right away.

Measuring Blood Pressure

Doctors measure blood pressure with a sphygmomanometer (sfig-mo-muh-NAH-muh-ter), which has a cuff that's wrapped around the upper arm and pumped up to create pressure. When the cuff is inflated, it compresses a large artery in the arm, stopping the blood flow for a moment. Blood pressure is measured as air is gradually let out of the cuff, which allows blood to flow through the artery again.

The doctor or nurse will also put a stethoscope over an artery to hear the first pulse as the blood flows through — this is the systolic pressure (or the pressure at the peak of each heartbeat). The diastolic pressure (the pressure when the heart is resting between beats) is noted when the sounds disappear.

When a blood pressure reading is taken, the higher number represents the systolic pressure and the lower number represents the diastolic pressure. For example: 120/80 (120 over 80) in an adult means that the systolic pressure is 120 and the diastolic pressure is 80.

Automated devices, which are good for screening, also can measure blood pressure, but a manual blood pressure measurement is more accurate.

As kids grow, their blood pressure increases from a systolic pressure of about 70-90 in an infant to adult values in a teenager. Among young kids, the "normal" range will depend on sex, age, and height; your doctor will be able to compare your child's blood pressure with national norms.

In kids, high blood pressure is defined as blood pressure greater than the 95th percentile for their age, height, and gender (in other words, 95% of kids of the same age, height, and gender will have blood pressure below this number).

It's not unusual for a first blood pressure reading to be high because a child is nervous, so the doctor will likely take three readings and use an average of the three to determine whether a child has high blood pressure or is at risk for developing it.

Some doctors use a test called ambulatory blood pressure monitoring in which a child wears a blood pressure cuff all day. Some consider it more accurate than blood pressure tests in the doctor's office because the child is less likely to be affected by any stress from the doctor visit.

Causes of High Blood Pressure

The causes of high blood pressure differ, depending on a child's age. The younger the child, the more likely the high blood pressure is linked to an illness.

High blood pressure in infants most commonly affects premature babies. Some newborns have high blood pressure because of problems with the kidneys (most commonly), lungs, heart, or circulatory system. These problems can include bronchopulmonary dysplasia, an immaturity of the lungs in premature babies; or conditions like coarctation of the aorta, a narrowing of part of the major blood vessel that carries blood away from the heart.

Among school-age kids and teens, hypertension usually is linked to excess weight. In some cases it's due to a problem with the kidneys, although other conditions — like abnormalities in the blood vessels and hormonal disorders — also can be responsible. If no specific cause is found, doctors call it "essential hypertension."

Some medications (such as steroids or oral contraceptives) can lead to high blood pressure, as can overconsumption of alcohol and illegal drugs.

Diagnosing High Blood Pressure

Because high blood pressure usually doesn't have noticeable symptoms, diagnosing it in kids can be tricky. Blood pressure varies a lot from day to day, so several blood pressure checks are often necessary to make the diagnosis (unless the pressure is very high, and then treatment is needed promptly).

The only way to know whether a child has high blood pressure is to get it checked regularly. It's often helpful to get blood pressure readings away from the doctor's office, like at school or at home if a blood pressure monitoring device is available. These readings should always be done when a child is resting.

Doctors usually start measuring blood pressure during routine checkups when kids are 3 years old. So it's important not to miss these appointments, particularly if your child is overweight or there's a family history of high blood pressure.

Treating High Blood Pressure

If an underlying illness is causing hypertension, treating that illness may be enough to get the blood pressure back to normal.

If there's no underlying illness, the doctor may recommend weight loss, exercise, reduced screen time (time spent watching TV, or using a computer or mobile devices), dietary changes, and even relaxation techniques. Kids with hypertension also should quit or never start smoking, which can worsen the long-term associated heart problems.

Here's what to focus on:

Weight loss: If your child is overweight, your doctor might recommend and monitor an ongoing weight-loss program that includes a minimum of 30 minutes of aerobic exercise every day.

Daily exercise: Being fit is a key part of blood pressure control. All kids with hypertension should exercise and play sports for 1 hour each day — with some activity (like jogging) most days and higher levels of activity (like running) 3 times a week. Usually, exercise is restricted only when hypertension is very severe. Kids with severe hypertension should not do any weight- or power-lifting, bodybuilding, or strength training until their blood pressure is under control and a doctor says it's OK.

Dietary changes: The doctor might recommend that your child's diet include more vegetables, fruits, low-fat dairy products, and fiber-rich foods, and fewer carbohydrates, fats, processed foods, and drinks with lots of sugar. The doctor also might recommend preparing low-sodium dishes and not adding salt to foods. Watch out for foods with lots of hidden salt (like bread, sandwiches, pizza, and many restaurant and fast food options).

Most doctors prefer not to prescribe medication for kids with mild hypertension. However, if lifestyle changes do not bring improvement, medicines might be needed.

Remember, while mild-to-moderate hypertension is rare in kids, over time it can damage the heart, kidneys, and blood vessels. Diagnosing and treating it will help prevent this damage.